Establishing an index of somatosensory acuity: comparison of three measures in adults

Speech production is directed by auditory and somatosensory targets that shape and update the motor plan through corresponding feedback channels (Guenther, 2016). Somatosensory feedback is instrumental in ensuring accurate articulator placement, as shown in studies where perturbed somatosensory feedback leads to reduced speech precision (Ringel and Steer, 1963; Gammon et al., 1971; Jones and Munhall, 2003). As no gold standard for measuring somatosensory acuity exists, the current study will compare three measures in 20 adults: (1) an oral stereognosis task (Steele et al., 2014) measuring tactile input received by the articulators; (2) a novel phonetic awareness task measuring the proprioceptive sense of articulator position; (3) a bite-block task with auditory masking (Zandipour et al., 2006) measuring the degree of compensation for perturbation using only somatosensory feedback. To test the hypothesis that participants with higher somatosensory acuity showed larger increases in production accuracy, participants’ scores on each task will be used to predict performance in an L2 vowel learning task (Li et al., in press). Three linear regression models will be fit, one for each somatosensory measure. The model that best explains change in production accuracy will be selected using the Akaike/Bayes Information Criteria. Establishing a valid measure of somatosensory acuity will enable future research to elucidate somatosensory influences on speech production.